Feed your birds suet. While most humans don't want a lot of fat in their diet, for birds in winter, fat is an excellent source of energy. Suet is, simply, fat. More specifically, it’s the fat that forms around the kidneys of beef cattle. Butchers remove this stuff, and back when every neighborhood had a butcher shop, they used to give it away to bird watchers. Then grocery stores got smart and started selling suet. You've probably seen it: large chunks of white fat wrapped in plastic in the meat case. Birds love suet, and it is especially valuable to insect-eating species during the winter, when insects are scarce or absent from much of the continent. Woodpeckers, bluebirds, warblers, chickadees, titmice, nuthatches, creepers, wrens, wrentits, jays, thrashers, mockingbirds and even sparrows and towhees are all big fans of suet.